This invention relates to a hydraulic centering device for a servo valve of a power steering device.
As shown in FIGS. 5 and 6, an input shaft 1 is joined with a torsion bar 4 via a balance pin 25 and is also joined with an output shaft 2. A valve sleeve 3 of a servo valve is rotatably inserted onto the input shaft 1 and is rotatably connected via a drive pin 5 to the output shaft 2. According to relative rotation of the input shaft 1 and the valve sleeve 3 the servo valve produces hydraulic pressure. The torsion bar 4 is secured via the balance pin 25 in the input shaft 1 such that when angle of the relative rotation is zero and the hydraulic pressure is balanced, torque of the torsion bar 4 becomes zero.
However, in this related art, once the hydraulic pressure becomes unbalanced, adjustment to balance the hydraulic pressure is impossible.